136 
U. S. P. R. R. EXP. AND SURVEYS-ZOOLOGY-—GENERAL REPORT. 
the curve, nearly parallel to each other. The distance from the orhit to the ante-orhital foramen 
is less, and the ante-orhital portion of the molar occupies nearly half the interval, instead of 
about one-fourth. The upper outline of the muzzle is less deeply indented on the middle of the 
nasals. The coronoid process is not so high, and its posterior outline is net hook-shaped and 
curving backwards, as in V. velox. These differences, however, after all, are not greater than 
may sometimes he seen in skulls of the same species, and it would not surprise me at all to 
ascertain, by careful comparison of skulls and skins of both animals, that Vulpes velox and 
corsac were one and the same species. The skulls of the two certainly resemble each other 
more closely than those of the American and European red foxes. 
The following description by Maximilian, of the Swift fox, in the Reise in das Innere Nord- 
Amerika , II, 1841-’44, taken from fresh specimens, will serve to throw light upon the history 
of the animal. 
Canis velox .—This species, scarcely half the size of the European fox, is shaped somewhat 
like it. The body is slender, as is also the head; the snout is pointed; the ear is large, pointed 
above, coated internally with whitish hairs. The eye is greenish-gray, with darker pupil. 
The color of whole upper parts and sides is a pleasant pale reddish-yellow, the hairs themselves 
being reddish-yellow at the roots, reddisfy-white at the tips, and marked subterminally 
with a little darker reddish gray-hrown. The tail is colored like the body, its tip, however, 
black. The color of the forehead and upper part of the head is a little darker than that of the 
hack, appearing slightly mixed with grayish-brown ; sides of the snout along the upper jaw, to 
the eye, blackish, the arch of the nose with a yellowish-red tinge; lower jaw and all under 
parts, as also the anterior face of the hind legs, whitish. In winter the animal is more of a 
pale grayish-brown, washed with brighter; all the hairs with decided white tips. 
Measurements. 
Feet. 
Inches. 
Lines. 
Total length________ 
2 
8 
7 
Tail to tip of hairs_ 
12 
Tail to end of Vertebras_ 
10 
2 
From tip of nose to anterior canthus__ 
2 
Length of orbital opening____ 
8 
Length from posterior canthus to the anterior base of the ear_ 
1 
7 
Height of external ear_________ 
2 
1 
Width of external ear at base___ 
1 
6 
Length of whole head___ 
4 
8 
The stomach is considerably curved; it was commonly full of fragments of skin, leather with 
hair, berries, remnants of mice, and grasshoppers, upon which the foxes of the prairies are 
necessitated to live on in great measure. The liver appears to be divided into seven greater 
and smaller folds; in the penis of the male is a hone 1 inch 7| lines long, shaped much like 
that of the wolf. 
The female brings forth from four to eight young, in holes, in March or April. 
